As materials for a support for a photographic material, polyester supports, such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), triacetyl cellulose, polystyrene, polycarbonate and polyolefin laminate are usually employed due to their excellent transparency. However, such polymer film has a hydrophobic surface, and therefore it is difficult to firmly bond a photographic emulsion layer comprising a hydrophilic polymer (hydrophilic colloid) mainly containing gelatin on the support of the polymer in the case of employing the polymer as the base film of the support for the photographic material.
Two processes can be utilised as a conventional technique which has been tried to overcome the above difficulty: (1) a process in which a photographic emulsion layer is directly formed on the support to obtain a high bonding strength after having provided the support with a surface activation treatment such as a corona discharge treatment, a glow discharge treatment, an active plasma treatment, a chemical treatment, a mechanical treatment, a UV treatment and similar and (2) a process in which an adhesion promoting layer is provided on the support subjected to the above surface treatment by coating, and then a photographic emulsion layer is formed thereon. The latter process is effective so that it is widely performed.
It is assumed that any of these surface treatments is effected by forming some polar groups on a surface of a base film which is originally hydrophobic and by increasing a cross linking density on a surface, and as a result, it is considered that the affinity of the components contained in the adhesion promoting layer with the polar group is increased or the bonding strength between the adhesion promoting layer and the base film is enhanced.
Some useful compositions for adhesion promoting layers include polymers containing vinylidene chloride such as vinylidene chloride/methyl acrylate/itaconic acid terpolymers or vinylidene chloride/acrylonitrile/acrylic acid and the like; butadiene-based copolymers, glycidyl acrylate or methacrylate containing copolymers, or maleic anhydride-containing copolymers. These and other suitable compositions described, for example, in U.S. Pat. Nos. 2,627,088; 2,698,240; 2,943,937; 3,143,421; 3,201,249; 3,271,178; 3,443,950 and 3,501,301 provide the required adhesion when applied before orientation but are not effective when applied on oriented support. The effectiveness of these adhesive materials may be enhanced by the use of swelling or attack agents such as resorcinol.
An alternative approach disclosed in U.S. Pat. No. 4,695,532 describes a discharge-treated polyester film support having coated directly thereon a crosslinked layer of an aqueous vinyl acrylate copolymer and gelatine mixture. Although this system has good adhesion before processing, the adhesion performance is severely degraded by photographic developing solutions.
U.S. Pat. No. 4,689,359 discloses a polymer composition comprising (a) 1-60 wt. % of recurring units from a vinyl monomer having a primary amine addition salt component and/or a vinyl monomer having an aminostyrene addition salt component; (b) 0-50 wt. % recurring units derived from a hydrophilic vinyl monomer and (c) 20-98 wt. % recurring units from a hydrophobic non-ionic vinyl monomer. The polymers are useful in aqueous coating compositions, for coating onto discharge-treated polyester film supports to form cross-linked layers to promote adhesion between the film support and other emulsion layers in photographic elements such as silver halide emulsion layers. U.S. Pat. No. 5,639,589 and EP Pat. Appl. No. 729,063 describe polyester photographic film supports comprising a surface coated with a subbing layer comprising a mixture of gelatin and the same polymer composition described in U.S. Pat. No. 4,689,359. High dry adhesion even with a thinner subbing layer and/or higher gelatin:polymer ratio is obtained.
U.S. Pat. No. 4,213,783 discloses subbing layers for polyester film supports comprising copolymers of 75 to 90 mole % of vinylidene chloride, 2 to 16 mole % of acrylonitrile or methacrylonitrile or a copolymerizable ester, 0.5 to 5 mole % of itaconic acid or a monoalkyl ester of itaconic acid, wherein the alkyl group contains 1 to 4 carbon atoms and 3 to 8 mole % of acrylamide, methacrylamide or N-methylol-acrylamide.
U.S. Pat. No. 5,532,118 discloses photographic element comprising a polyester film support having coated thereon a self-crosslinkable polyurethane derived from an isocyanate terminated prepolymer extended with an aliphatic polyamine and end-capped with N-methylol hydrazide groups, the prepolymer being derived from a diisocyanate and a polyester polyol and having pendant water dispersing, carboxylic salt groups on the polymer chain. The photographic element disclosed therein exhibits good wet adhesion and dry adhesion, before and after photographic processing.
U.S. Pat. No. 4,329,423 discloses a light-sensitive photographic film, which comprises a support base, a copolymeric subbing layer applied to at least one surface of said base and a light-sensitive photographic emulsion layer bonded directly to the copolymeric subbing layer, said copolymeric subbing layer comprising a copolymer prepared from a comonomer mixture consisting essentially of 35 to 55 mole % acrylic acid or a lower alkyl ester, 35 to 55 mole % methacrylic acid or a lower alkyl ester thereof, and 1 to 15 mole % of itaconic acid or itaconic anhydride and 0 to 8 mole % of additional monomer selected from the class consisting of acrylamide, methacryl-amide, N-methylol acrylamide, etc.
U.S. Pat. No. 4,123,277 discloses a photographic element which comprises a support having superimposed thereon an adhesion promoting layer of a composition comprising a copolymer containing a) an N-alkanolamide moiety or an N-alkoxyal-kylamide moiety, b) a monomer which provides a carboxyl group and c) a hydrophobic monomer, and a hydrophilic colloid layer coated on said adhesion promoting layer, said hydrophilic colloid layer containing light-sensitive silver halide emulsion, physical development nuclei as used in a diffusion transfer process or diazo compounds.
U.S. Pat. No. 5,510,233 discloses a photographic material having a first and a second adhesion promoting layer and an emulsion layer coated in this order on a same side of a polyester support base, in which the first adhesion promoting layer is a hardened layer comprising polyurethane latex and an ethoxy compound or a dichloro-s-triazine derivative, and the second adhesion promoting layer is a hydrophilic colloid layer substantially consisting of gelatin. The polyurethane latex has breaking elongation lower than 300% or tensile stress of at least 130 kg/cm2 at 100% elongation. The composition of the adhesion promoting layers improves adhesion between emulsion layer and the support and prevents delamination even under prolonged storage at high humidity. condition. It also prevents emulsion from cracking even at extremely low humidity storage. Additional advantage is the resistance against reticulation at the processing and the background clarity of the processed images.
U.S. Pat. No. 4,339,531 discloses a coated film base suitable for coating with a light-sensitive photographic emulsion layer comprising a self-supporting film of a synthetic linear polyester and a continuous layer applied to at least one surface of said self-supporting film comprising a water-insoluble polymer of (a) styrene or a derivative of styrene, (b) a comonomer selected from acrylic acid, methacrylic acid or a derivative of acrylic acid or methacrylic acid and (c) a copolymerizable sulphonated ethylenically unsaturated comonomer. Photographic emulsions adhere strongly to the layer, especially after corona discharge treatment.
U.S. Pat. No. 4,571,363 describes a melt-extruded, oriented, self-supporting polyester film having an extensive crosslinked acrylic adhesion promoter coating on one or both sides. The adhesion promoter coating consists essentially of a crosslinked copolymer containing at least 50% by weight of acrylic and/or methacrylic monomers, from 1% to 15% by weight of a comonomer capable of intermolecular crosslinking upon the application of heat, and up to 49% by weight of halogen-free monoethylenically unsaturated monomers copolymerizable therewith.
PCT Patent Application No. 94-13,481 discloses a biaxially oriented copolyester film coated on one or both sides with vinyl acetate polymers which render the copolyester film surface receptive to additional reprographic or matte coatings applied thereto.
British Patent No. 1,496,967 discloses a polymeric priming layer applied to at least one side of a support film and a resinous hydrophilic layer applied thereto, the priming layer comprising a complete or partial salt of a polymer of acrylic and/or methacrylic acid that has been crosslinked with the aid of a crosslinking agent.
U.S. Pat. No. 5,514,528 discloses a photographic element having a polyester support carrying a light-sensitive layer on one surface and an antistatic layer containing a conductive metal oxide in a hydrophilic binder on the other surface. A subbing layer consisting of an addition or condensation polymer is provided between the support and the antistatic layer. Preferably the subbing layer is an addition polymer containing a vinylidene chloride/acrylonitrile copolymer or vinylidene chloride/acrylonitrile/acrylic acid terpolymer. The element is resistant to formation of minute areas where a loss of adhesion occurs between adjacent layers, in the backing layers.
It is desirable to provide polyester film supports having improved adhesion of emulsion layers coated thereon before, during and after photographic processing.